Backup protection for comparator systems having faulted supply



Sept. 26, 1950 A. CHEVALLIER 2,523,813

BACKUP PROTECTION FOR COMPARATOR sys'rms mvmc FAULTED SUPPLY OriginalFiled April 5, 1945 5 Shee'ts-Sheet 1 1221 M1 LA 7/1 1;1 Zg z? b as; Of421 d d2 2 025 623 5 INVENTOR ANDRE GHEVALLIER AGENTS Sept. 26, 1950 A.CHEVALLIER 2,523,813

BACKUP PROTECTION FOR COMPARATOR SYSTEMS HAVING FAULTED SUPPLY OriginalFiled April 5, 1945 5 Sheets-Sheet 2 INVENTUR AN DR E CH EWLL'ER U3g-34AM AGENTS Sept. 26, 1950 A. CHEVALLIER 2,523,813

BACKUP PROTECTION FOR COMPARATOR SYSTEMS HAVING FAULTED SUPPLY OriginalFiled April 5, 1945 5 Sheets-Sheet 5 AN DR E GHEVALLI ER fljfi A GE'NTSSept. 26, 1950 A. CHEVALLIER 2,523,813

BACKUP PROTECTION FOR COMPARATOR SYSTEMS HAVING FAULTED SUPPLY OriginalFiled April 5, 1945 5 Sheets-Sheet 4 INVENTDR ANDRE GHEVALLIER gab-gmAGENTS Sept. 26, 1950 A. CHEVALLIER 2,523,813

BACKUP PROTECTION FOR COMPARATOR SYSTEMS HAVING FAULTED SUPPLY OriginalFiled April 5, 1945 5 Sheets-Sheet 5 3 v J 5 T j J 1 2 2);; l 1 J J 1 11 Z? 1 l 7 121716 L lji y r 'j 11 l ja gtg l jg ---a fij iy 12m; gig? 102 0a l .1

TA? m 1Z1 -J\MNWV\MIWW INVENTDR ANDRE CHEVALLIER AGENTS Patented Sept.26, 1950 BACKUP PROTECTION FOR COMPARATOR SYSTEMS HAVING FAULTED SUPPLYAndr Chevallier, Paris, France, assignor to Societe Union DElectricite,Paris (Seine), France,

a society of France Original application April 5, 1945, Serial No.

Divided and this application October 25, 1947, Serial No. 782,195. InFrance September 10, 1943 13 Claims.

The .present invention relates to methods and apparatus for measuring orcomparing periodic, and in particular sinusoidal functions or factors,of the kind described in my prior U. S. patent application Ser. No.586,778, filed April 5, 1945, for Improvements in Device for Measuringand Comparing Functions of which the present application is a division.

Such an apparatus essentially includes comparators supplied with thesinusoidal factors in question.

The chief object of the present invention is to provide an apparatus ofthe kind in question which is capable of working correctly even when forsome reason one of the factors to be compared cannot be transmitted tothe corresponding comparator device (for instance in the case of a deadline or of a failure in the transmission between comparator devices).

Preferred embodiments of the present invention will be hereinafterdescribed with reference to the accompanying drawings, given merely byway of example, and in which:

Fig. 1 is a diagram showing the arrangement of the protection apparatusin several sections of a line;

Fig. 2 diagrammatically shows a discriminative protection systemaccording to the invention;

Fig. 3 is a diagram of one of the comparator devices included in thissystem;

Fig. 4 shows the current-voltage curve of a contact rectifier, thiscurve being given to illustrate the working of rectifiers such as shownby Fig. 3;

Fig. 5 is a diagram given for the same purpose;

Fig. 6 shows a portion .of a system of the kind illustrated by Fig. 2,made according to one of the features of the invention;

Fig. 7 is a detailed showing of a protection system made according tothe invention;

Fig. 8 is a view of a portion of the same device made according toanother embodiment;

Fig. 9 shows the same portion of the comparator device, embodying otherfeatures of the invention;

Fig. 10 is an explanatory diagram relating to the system of Fig. 11;

Fig. 11 shows a portion of the system of Fig. '7, according to amodification of the invention;

Fig. 12 diagrammatically shows a voltage limiting device to be includedin such a system, this device being made according to the invention;

Fig. 13 is a diagram of the voltage on the input and output sides ofthis limiting device.

In the following description, it will be supposed that the invention isapplied to the protection of an energy transmission network.

Fig. 1 diagrammatically shows, by Way of example, a line L supposed tobe fed at both ends by groups of machines M1 M2. Several sections areillustrated at AB, CD, EF, with their circuitbreakers d1, di, d2, d'z,d3, ds, etc.

If a fault occurs, for instance, at T, in section CD, the currents i1,i'i in section AB remain in phase, same as the currents is, is insection while the currents i in the section CD where the fault hasoccurred are reversed with respect to each other.

The method described in the above mentioned application .provides forcomparators at the extremities of each section, to detect this reversaland control the release of the corresponding circuit-breakers.

Fig. 2 diagrammatically shows the equipment for one line section AB,with circuit-breakers DA-DB. The comparators are illustrated at BCA andB03; they are both acted upon by the currents I1 and I2 or by the powersat the respective ends of the section, for instance through intensitytransformers TA and TB, or by voltages in and a2 proportional to thesecurrents or powers and, in phase therewith. For instance, eachcomparator has two inputs, one directly connected to the transformer (TAor TB) located at the same end of the section this comparator and theother connected (through distance transmission means, such as lines inor IA) with the transformer (TB or TA) at the other end of the section.Comparator device BCA is adapted to act upon the coil bA ofcircuit-breaker DA, and comparator device BCB upon the coil be ofcircuit breaker DB.

Fig. 3 shows a comparator device of the dry rectifier type such as thosedescribed in the above mentioned prior application.

It comprises two circuits (each preferably double in order to rectifyboth alternations) in one of which the alternating potentials in and 112are added together (upper circuit on the diagram of Fig. 3), whilst theyare subtracted from one another in the other (lower circuit). To thisend, it suffices to make use of transformer devices, of which only thesecondaries have been shown on Fig. 3, it being understood that theprimary circuits are arranged in any suitable manner such in particularas described in the above mentioned prior application. The rectifiersare shown at T1, T2, T3, T4.

Each of the circuits includes a resistance R and the whole of said tworesistances R is connected (I in series with a resistance p so thatthere is finally obtained, between two points a and b, a potentialdifference in one direction or the other according as potentials 'LLl,uz are in phase or not.

It is then possible to operate a relay Rd mounted to control thecorresponding circuitbreaker, for example by using the potentialdifference between a and b to polarize one or more electronic tubes(multi-electrode valves, thyratrons, etc.) arranged in such manner as tooperate the said relay.

In the embodiment of Fig. 3 the circuit-breaker is combined with a relayRd controlling the circuit of the coil in of breaker DA. Tube Z isinserted in the circuit of the Winding of said relay Rd and has its gridand filament connected to points a and b, respectively. In normalworking conditions, that is to say when potentials in and Liz are inphase, point a is positive with respect to point b, so that no currentfiows through valve 1 (relay Rd is therefore inactive). As soon as afault takes place, the reversal resulting therefrom in one of thepotentials in and 142 causes a reversal of the current between a and bso that point a; becomes negative with respect to point b, relay Rd isbrought into play and the corresponding circuit-breaker is tripped open.

A capacitor C may be provided across the terminals of p to permit ofgiving the time constant the minimum value and thus ensuring the maximumspeed of operation. I may also, in order to diminish the time constant,dispose the trip coil "01 (Fig. 8) directly in the circuit of the valveor of the thyratron.

In Fig. 8 which shows an embodiment in which a thyratron is used, Pdesignates the grid polarisation battery, provided with a resistance r.A switch is provided at 90 in the anode circuit for cutting the currenttherethrough after release of the circuit-breaker, said switch being forinstance operative by said circuit-breaker.

I will now explain the operation of the rectifiers of Figures 3 and 8.

It is known that the current-potential curve of these rectifiers is ofparabolic form at the origin (Fig. 4) then becoming progressivelystraight; for values of the potential u greater than a lower limit 240,it may be considered as rectilinear.

It has been shown in the above mentioned prior application that, in theparabolic portion, the mean rectified current passing throughresistances p1, p2 (Fig. 3) is of the form:

i=47cu1u2 If ur and M2 are themselves of the form of:

that is to say, proportional to the phase difference between currents I1and I2. Which shows that, as above stated, a defect occurring on theline and causing the reversal of one of the currents I1, I2 (one ofthese currents being thus in phase difference of 1r) has for effect alsoto reverse the mean current in said resistances:

It has been found, according to my invention, that the same reversal isobtained with the device working along the straight portion of thecharacteristic.

This results from the fact that the mean current jm flowing throughresistances p1 and pz is then:

This is a periodic function of a period equal to 21r. Therefore if (p ischanged to 1r+ y'm becomes ?m.

Thus whether the system is working along the parabolic portion or thestraight portion of the characteristic curve, the same operation takesplace: to wit, the reversal of the mean current in response to thereversal of only one of the potentials mm. It is to be furthermore notedthat if the two potentials are reversed (Fig. 5) the angle between thesetwo potentials remain (p so that the direction of the mean current isnot modified.

It should also be pointed out that the more or less complex form ofpotentials in U2 is without influence on the result, since thedevelopment in Fourier series or" the function representing therectified current shows that the only terms remaining after thisrectification, apart from the constant terms (mean value im) are eventerms in Zwt, 4wt, etc., the mean value of which from 0 to 1r is zero.

It has been supposed, in the preceding description, that two voltages inand uz were permanently available at the terminals of the comparatordevices such as BCl or BCz. But is may happen that one of these termsdoes not exist or is not transmitted. This is the case, in particular:

(a) When the line AB, C-D, E- -F is fed with current only from one endthereof; or

(b) When there is a breakdown in the transmission ZB between thecomparator devices.

In both of these cases, the comparison cannot take place, since thedirect current supplied by the comparator devices is zero and indicatesno potential difference between points a and 1).

According to my invention, means are provided for obviating thisdrawback, said means being adapted, even in the above mentioned cases,to supply the comparator, in the occurrence of a fault on the line, withtwo input voltages in opposition, which trip the circuit-breakers.

Although it is possible, for someone skilled in the art, to providevarious means of this kind, it has been found that it suiiices,according to a very simple embodiment, to provide at each end of theline and on each phase, a voltage having 55 a phase difference of withrespect to the voltage of this phase.

This is due to the fact that, if a fault occurs one the line, thecurrent I is caused to lag by practically ceives a voltage in or uz thatlags by behind the star grouping voltage of this phase.

If, now, there is applied to the same comparator device an auxiliaryvoltage us with a leading phase difference of this last mentionedvoltage has a phase difference of 11' with voltage in or m... Thereforeit causes release to take place.

A diagram of a device for carrying out this principle is shown by Fig.6.

Comparator device B01 is arranged in the same manner as that of Fig. 2,but it is combined:

(a) On the one hand with a first relay Rm1 located at the entrance ofthe transmission line IE and adapted, when no current is being fedthrough said line, (which applies as well to the case of the line beingdead as to that of a breakdown in transmission In), to open contacts C1,that is to say to isolate this transmission, and to close contacts C1which connect the comparator device with a dephasing device D1 whichsupplies the auxiliary voltage as in phase difference of ahead of thestar grouping voltage; and

(b) On the other hand with a second relay RM1, of the intensity maximumtype, having its winding in series with transformer TA and its contactsinterposed between device D1 and contact C1, this relay being such thatit establishes connection between said device D1 and said contacts Cionly when intensity I1, under the effect of a fault, exceeds apredetermined maximum value.

The various contacts are shown in Fig. 6 in their positionscorresponding to normal operation, in the absence of a fault and whenthe line is live.

Every time the line is dead or there is a breakdown in transmission ZB,relay R7711 comes into the other position. When a fault occurs, theoperation of relay RM1 ensures the desired instantaneous tripping of theprotection apparatus.

But auxiliary voltage Ila may be obtained. in a different manner. Forinstance, I may take advantage of the fact, illustrated by Fig. 10,that, in the case of a three-phase system the voltages in the threephases of which are shown at in, uz, m, a dephased voltage such as thatabove designated by Ma is obtained with respect to the voltage of onephase in by taking the voltage between the two other phases uz and us.

Fig. 11 shows an arrangement based on this principle. This figure isintended to show only the connections for supplying the compensatordevices B01, BC2, B03 with the desired auxiliary voltages Mal, UaZ,uali. The connections for normal operation have not been shown on thisfigure, nor the circuits for controlling the circuitbreakers and thecircuits for operating relays Rm, RmZ, Rm. Fig. 11 shows that athree-phase system of conductors, designated by the voltages u1, U2, itsexisting therein, is connected to the line I, 2, 3 through voltagetransformers Tpl, T z, T 13 so that voltages in, M2, us are of suitablevalues to be fed to the comparator devices B01, B02, BC3.

The input of each of said comparator devices will be supplied, on theone hand, through transformers TA1, TAz, 'IAs, as usual, and on theother hand, when one of the relays Tml T1112, T1113 are energized, witha voltage us proportional to the difference between the two otherphases. For instance relay Rm1 will connect the corresponding inputterminals of 1301 with conductors 112' and us. It should be noted thatthe comparator devices must be adjusted in such manner that they cannotcause tripping of the circuit-breakers when there is no voltage betweenpoints a and b of said comparator devices, especially in one of the twocases above mentioned, to wit dead line or breakdown in thetransmission. For this purpose, it suffices, considering for instancethe case of Fig. 3, suitably to bias the grid of tube Z so that relay Rdcannot be energized in the absence of a difference of potential betweena and b. Besides, it may be advantageous, according to still anotherfeature of the invention, to provide indicator means for checking theoperation 0 the apparatus.

Such means will for instance indicate, in a visual, acoustic, or otherway, the absence of a potential difference between the terminals ofresistance p, that is to say between points a and b of the comparatordevice of Fig. 3. According to an embodiment illustrated by Fig. 9, Iprovide in the circuit of tube Z (see Fig- 3'), a resistance 20connected across the filament grid space of an auxiliary tube 30 adaptedto control from a distance an alarm device 40 through a relay 50.

Under normal transmission conditions (a positive, 2) negative), tube 1is conducting and there is a small current flowing through resistance20. Therefore tube 30 is conducting and relay 5D is kept energized. Thiscurrent through resistance 20 disappears when for some reason thecomparator device ceases to work and there is no difference of potentialbetween a and b. The voltage across tube 30 then drops to zero, relay 50is de-energized and alarm is given by indicator 50.

The present invention also includes another feature, relating to thevoltage limiting devices to be interposed on the input side of thecomparator devices as indicated in the above mentioned priorapplication. If it is true that the quickness of tripping isproportional to the mean current rectified in the comparator devices,which current is a function of voltages a1 and uz, which themselvesincrease simultaneously with currents I1 and I2, it is however necessaryto limit these Voltages to suitable values. It is possible to make usefor this purpose of limiting devices of any known type, provided thattheir time constants are as low as possible.

For instance, it will be advantageous to make use of a device of thekind of that of Fig. 12, in which, in order to obtain a reduced voltageUr from the voltage a, rectifiers such as d1, d2, are arranged inparallel. 1

Fig. 12 shows that the source S that supplies voltage u feedsresistances R1 and R2 (R2 representing the utilization resistance) with,in shunt, rectifiers 111 and (12 the current-voltage characteristiccurve of which is parabolic. Therefore, the resistance of theserectifiers has a curve of hyperbolic shape, that is to say decreasessimultaneously with the voltage at the terminals. Under theseconditions, the drop of potential across resistance R1 increases muchmore rapidly than the value of voltage u. Besides, it should be notedthat this drop of potential is the greater as the value of theresistances of rectifiers d1 and d2 is smaller.

Finally, for the utilization voltage Ur, a curve is obtained of theshape of that shown at F on Fig. 13 (where F represents the initialvoltage u). r

It should be noted that the flattened curve F that is thus obtained maybe considered as the sum of sine curves the frequencies of which are wt,Zwt, 3wt, 4wt, etc., but in which the rectifying effect has eliminatedall odd numbered harmonics. Therefore, there remain only evennumberedharmonics which, as above stated, are without influence on thecomparator device, since their mean value in a half-period is zero.

Finally, according to still another feature of the invention, dephasersmay be provided for correcting the angle of phase difference that mayresult from transmission TR and also for taking into account the factthat the angle of phase difference between I1 and I2 is slightly smallerthan 1r when a fault occurs and tends to be more or less differenttherefrom according to the conditions of loading of the line at thistime. The intensity of the mean current rectified in the comparatordevices, upon which the quickness of the release depends, varies in factin inverse ratio to the angle (p between I1 and I2, so that it isparticularly interesting to compensate for the phase difference that maybe brought about for the above mentioned reasons.

The essential elements of a protection system according to the inventionhaving thus been described, it seems of interest to give, by way ofexample, a general diagram in which these elements are explicitly shown.

In Fig. 7, which constitutes such a diagram, I have shown at:

TAi, 'IAz, TAs, the intensity transformers intended to impress thevoltages such as ur, uz, u: on the comparator devices;

Tpi, Tpz, T233, the potential transformers for the feed of the dephasersD1, D2, D3

bAl, bA2, bAB, the trip coils of the circuit-breakers;

BCi, BC2, B03, the comparator devices;

TR, the transmission between comparator devices;

RE', the receivers of this transmission;

L1, L2, L3, the voltage limiting devices;

RMi, RM2, RMa the current maximum relays;

D1, D2, D3, the dephasers that suppl the auxiliary voltage Ma having aphase difference of ahead of the corresponding star grouping voltages;

Rmi, Rmz, Rma, the relays which operate contacts CC and are intended tocoact with RM, as above stated;

d1, d2, (13, the dephasers for correcting the phase difference anglevariations resulting from at least one of the above mentioned causes.The transmission system may be of any suitable type. Transmission bymeans of carrier currents flowing through the network itself is wellknown.

But other systems may be used. If, for instance,

six lines such as [A and In (Figs. 2 and 6) are available between theends A and B of the section, bilateral transmission of the three abovementioned voltages is very simple since it can be performed in the 50period system directly. If only a telephonic pair (la it, Fig. 7) isavailable, it is possible to transmit voltages at different musicalfrequencies modulated by said voltages.

Musical frequency transmitting and receiving sets TTA and RTB (Fig. '7)will be necessary at each section end.

Anyway, a protection system made as above described and as illustratedby the appended drawings complies with all the requirements of practice,as hereafter briefly set forth:

(a) If there is a fault inside a section, it is immediately detected bythe reversing of the current direction between points a and b (Figs. 3and 8), as above indicated. Operation is practically instantaneous asthe time constant of the various circuits is extremely low;

(b) If there is a fault on the outside of the section that is beingconsidered, the currents at the ends of this section are not reversed sothat the potential difference between a and b remains in the samedirection, that is to say negatively polarizes the grid of the controltube, the circuit breakers therefore remaining locked in their closedposition. Besides, it should be noted that the grid polarization is thegreater as the fault current is more considerable;

(c) The system works as above indicated, whatever be the nature of thefault (between one phase and the earth, between two phases, symmetricalbetween the three phases, or between the three phases and the earth) (d)If synchronism is broken, the currents at the'ends of the line sectionsare not reversed with respect to each other, the voltage between a and bremains positive and the release coil is not fed; on the other hand, ifa fault occurs while the synchronism is being broken, the currents arereversed and the release orderis transmitted;

(e) Protection is still ensured even in the case of the line being deador in that of a lack of transmission between comparator devices, owingto the provision of the special means above described;

(j) The working of the devices remains correct even in case of lack oftransmission since the absence of a difference of potential betweenpoints a and b does not result in the release of the protectionapparatus taking place;

(9) Finally, owing to the supplementary checking means above described,it is possible to know at any time if the protection apparatus are ingood working order.

The protection system according to the invention eliminates allmeasurement relays such as directional watt-metric relays, minimumimpedance relays, and so on. The only relays that are made use of arerelays of the telephonic type or of the current maximum type.

Furthermore, this protection system does not require the provision of aphase sorter when it is necessary or desired to perform automaticreengagement phase by phase.

In a general manner, while I have, in the above description, disclosedwhat I deem to be practical and efficient embodiments of my invention,it should be well understood that I do not wish to be limited thereto asthere might be changes made in the arrangement, disposition and form ofthe parts without departing from the principle of the present inventionas comprehended within the scope of the accompanying claims.

What I claim is:

1. In connection with an electric system traversed by at least onealternating current and divided into sections, the combination of acomparator device located at one end of a section of said electricsystem, means, including a coupling between said end of said section andsaid comparator device and distance transmission means between the otherend of said section and said comparator device, for transmitting fromthe respective ends of said section to the input of said comparatordevice voltag values proportional to the factors to be compared,respectively, an apparatus coupled with saidcomparator device to beoperated by it in response to a reversing in the phase relation betweensaid respective factors, means, at said first mentioned end of saidsection, for supplying an auxiliary voltage in leading phase differenceof 90 with the voltage at said end of said section, and means forconnecting said auxiliary voltage supply means with said comparatordevice in response to the occurrence of a fault in said section during aperiod for which one of said voltage values is not transmitted to saidcomparator means.

2. In connection with an electric distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection apparatus at one end of said section, means coupled with theoutput of said comparator device for operating said protection apparatusin response to a reversing in the phase relation between thesimultaneous values of said voltages, means, at said first mentioned endof said section, for supplying an auxiliary voltage in leading phasedifference of 90 with the voltage at said end of the section, and tworelays in series for connecting said auxiliary voltage supply means withsaid comparator device, one of said relays being operative in responseto a failure of said transmission means and the other in response to theoccurrence of a fault in said section of said system.

3. In connection with an electric distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand, said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection apparatus at one end of said section, means coupled with theoutput of said comparator device for operating said protection apparatusin response to a reversing in the phase relation between the simulaneousvalues of said voltages, means, constituted b a dephaser coupled withsaid electric system, at said first mentioned end of said section, forsupplying an auxiliary voltage in leading phase difierence of 90 withthe voltage at said end of the section and means for connecting saidauxiliary voltage supply means with said comparator device in responseto the occurrence of a fault in said section during a breakdown of saiddistance transmission means.

4. In connection with an electric distribution system traversed by atleast one alternating current and divided in o sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the twoends of said section, respectively, aprotection apparatus at one end of said section, means coupled with theoutput of said comparator device for operating said protection apparatusin response to a reversing in the phase relation between thesimultaneous values of said voltages, means, constituted by a dephasercoupled with said electric system, at said first mentioned end of saidsection, for supplying an auxiliary voltage in leading phase differenceof with the voltage at said end of the section, and two relays in seriesfor connecting said auxiliary voltage supply means with said comparatordevice, one of said relays being operative in response to a failure ofsaid transmission means and the other in response to the occurrence of afault in said section of said system.

5. In connection with an electri distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection circuitbreaker at one end of said section, means coupled withthe output of said comparator device for releasing said circuit-breakerin response to a reversing in the phase relation between thesimultaneous values of said voltages, means, at said first mentioned endof said section, for supplying an auxiliary voltage in leading phasedifference of 90 with the voltage at said end of the section, means forconnecting said auxiliary voltage supply means with said comparatordevice in response to the occurrence of a fault in said section during abreakdown of said distance transmission means, and means for opposingthe release of said circuit-breaker in case of absence of voltage acrossthe output terminals of said comparator device.

6. In connection with an electric distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection circuitbreaker at one end of said section, means coupled withthe output of said comparator device for releasing said circuit-breakerin response to a reversing in the phase relation between thesimultaneous values of said voltages, means, at said first mentioned endof said section, for supplying an auxiliary voltage in leading phasedifi'erence of 90 with the voltage at said end of the section, tworelays in series for connecting said auxiliary voltage supply means withsaid comparator device, one of said relays being operative in responseto a failure of said transmission the output terminals of saidcomparator means.

7. In connection with an electric distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection circuitbreaker at one end of said section, a relay forreleasing said circuit-breaker, an electronic tube for operating saidrelay, an input circuit for said tube coupled with the output of saidcomparator device so as to release said circuit-breaker in response to areversing in the phase relation between the simultaneous values of saidvoltages, means in said input circuit for placing a bias on the grid ofsaid tube adapted to prevent operation of said relay by said tube whenno voltage drop is impressed across the filament-grid space of said tubeby said input circuit, means, at said first mentioned end of saidsection, for supplying an auxiliary voltage in leading phase differenceof 90 with the voltage at said end of the section, and means forconnecting said auxiliary voltage supply means with said comparatordevice in response to the occurrence of a fault in said section during abreakdown of said distance transmission means.

8. In connection with an electric distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection circuitbreaker at one end of said section, a relay forreleasing said circuit-breaker, an electronic tube for operating saidrelay, an input'circuit for said tube coupled with the output of saidcomparator devic so as to release said circuit-breaker in response to areversing in the phase relation between the simultaneous values of saidvoltages means in said input circuit for placing a bias on the grid ofsaid tube adapted to prevent operation of said relay by said tube whenno voltage drop is impressed across the filament-grid space of said tubeby said input circuit, means, at said first mentioned end of saidsection, for supplying an auxiliary voltage in leading phase differenceof 90 with the voltage at said end of the section, and two relays inseries for connecting said auxiliary voltage supply means with saidcomparator device, one of said relays being operative in response to afailure of said transmission means and the other in response to theoccurrence of a fault in said section of said system.

9. In connection with an electric distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection circuitbreaker at one end of said section, means coupled withthe output of said comparator device for releasing said circuit-breakerin response to a reversing in the phase relation between thesimultaneous values of said voltages, means, at said first mentioned endof said section, for supplying an auxiliary voltage in leading phasedifference of with the voltage at said end of the section, means forconnecting said auxiliary voltage supply means with said comparatordevice in response to the occurrence of a fault in said section during abreakdown of said distance transmission means, means for opposing therelease of said circuit-breaker in case of absence of voltage across theoutput terminals of said comparator device, and signal means forindicating the absence of voltage drop across the output terminals ofsaid comparator device.

10. In connection with an electric distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection circuitbreaker at one end of said section, means coupled withthe output of said comparator device for releasing said circuit-breakerin response to a reversing in the phase relation between thesimultaneous values of said voltages, means, at said first mentioned endof said section, for supplyin an auxiliary voltage in leading phasedifference of 90 with the voltage at said end of the section, two relaysin series for connecting said auxiliary voltage supply means with saidcomparator device, one of said relays being operative in response to afailure of said transmission means and the other in response to theoccurrence of a fault in said section of said system, means for opposingthe release of said circuitbreaker in case of absence of voltage acrossthe output terminals of said comparator device, and signal means forindicating the absence of voltage drop across the output terminals ofsaid comparator device.

11. In connection with an electric distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection circuitbreaker at one end of said section, a relay forreleasing said circuit-breaker, an electronic tube for operating saidrelay, an input circuit for said tube coupled with the output of saidcomparator device so as to release said circuit-breaker in response to areversing in the phase relation between the simultaneous values of saidvoltages, means in said input circuit for placing a bias on the grid ofsaid tube adapted to prevent operation of said relay by said tube whenno voltage drop is impressed across the filament-grid space of said tubeby said input circuit, a resistance in said input circuit, a signaldevice, and an electronic tube for operating said signal device havingits filament-grid space connnected across said resistance, means, atsaid first mentioned end of said section, for suppling an auxiliaryvoltage in leading phase difference of 90 with the voltage at said endof the section, and means for connecting said auxiliary voltage supplymeans with said. comparator device in response to the occurrence of afault in said section during a breakdown of said distance transmissionmeans.

12. In connection with an electric distribution system traversed by atleast one alternating current and divided into sections, the combinationof a comparator device located at one end of a section, means, includinga coupling between said end of said section and said comparator deviceand distance transmission means between the other end of said sectionand said comparator device, for transmitting to the input of saidcomparator device the values of the voltage in said system takensimultaneously at the two ends of said section, respectively, aprotection circuitbreaker at one end of said section, a relay forreleasing said circuit-breaker, an electronic tube for operating saidrelay, an input circuit for said tube coupled with the output of saidcomparator device so as to release said circuit-breaker in response to areversing in the phase relation between the simultaneous values of saidvoltages, means in said input circuit for placing a bias on the grid ofsaid tube adapted to prevent operation of said relay by said tube whenno voltage drop is impressed across the filament-grid space of said tubeby said input circuit, a resistance in said input circuit, a signaldevice, and an electronic tube fOr operating said signal device havingits filament-grid space connected across said resistance, means, at saidfirst mentioned end of said section, for suppling an auxiliary voltagein leading phase diilerence of 90 with the voltage at said end of thesection, and two relays in series for connecting said auxiliary voltagesupply means with said comparator device, one of said relays beingoperative in response to a failure of said transmission means and theother in response to the occurrence of a fault in said section of saidsystem.

13. In connection with an electric system traversed by at least onealternating current and divided into sections, the combination of aprotection circuit-breaker at one end of said section, a phasecomparator device at said end of said section having two inputs and oneoutput, said output being connected with said circuit breaker and saidcomparator device being adapted to operate said circuit-breaker inresponse to the supply of electric factors in phase opposition to eachother to the respective inputs of said device, means including acoupling between said end of said section and one input of saidcomparator device and distance transmission means between the other endof said section and the other input of said comparator device fortransmitting from the respective ends of said section to the tworespective ends of said device voltage values proportional to the valuesof an electric factor at said ends of said section, means at said firstmentioned end of said section for suppling said comparator device withan auxiliary voltage in predetermined phase diiference with the voltageat said first mentioned end of the section to place the respectiveinputs of said device in phase opposition to each other in response tothe occurrence of a fault in said section, and means for bringing saidauxiliary voltage supply means into action in response to the occurrenceof a fault in said section during a period for which said distancetransmission means are out of operation.

ANDRE CHEVALLIER.

REFERENCES CITED The following references are of record in the file ofthis patent:

V UNITED STATES PATENTS Number

